[PATCH v7 04/22] vfio: Accept vfio device file in the KVM facing kAPI

[Yi Liu <yi.l.liu@xxxxxxxxx>]

This makes the vfio file kAPIs to accept vfio device files, also a
preparation for vfio device cdev support.

For the kvm set with vfio device file, kvm pointer is stored in struct
vfio_device_file, and use kvm_ref_lock to protect kvm set and kvm
pointer usage within VFIO. This kvm pointer will be set to vfio_device
after device file is bound to iommufd in the cdev path.

Reviewed-by: Kevin Tian <kevin.tian@xxxxxxxxx>
Reviewed-by: Jason Gunthorpe <jgg@xxxxxxxxxx>
Tested-by: Terrence Xu <terrence.xu@xxxxxxxxx>
Tested-by: Nicolin Chen <nicolinc@xxxxxxxxxx>
Tested-by: Matthew Rosato <mjrosato@xxxxxxxxxxxxx>
Signed-off-by: Yi Liu <yi.l.liu@xxxxxxxxx>
---
 drivers/vfio/vfio.h      |  2 ++
 drivers/vfio/vfio_main.c | 18 ++++++++++++++++++
 2 files changed, 20 insertions(+)

diff --git a/drivers/vfio/vfio.h b/drivers/vfio/vfio.h
index 56ad127ac618..e4672d91a6f7 100644
--- a/drivers/vfio/vfio.h
+++ b/drivers/vfio/vfio.h
@@ -18,6 +18,8 @@ struct vfio_container;
 
 struct vfio_device_file {
 	struct vfio_device *device;
+	spinlock_t kvm_ref_lock; /* protect kvm field */
+	struct kvm *kvm;
 };
 
 void vfio_device_put_registration(struct vfio_device *device);
diff --git a/drivers/vfio/vfio_main.c b/drivers/vfio/vfio_main.c
index 748bde4d74d9..cb543791b28b 100644
--- a/drivers/vfio/vfio_main.c
+++ b/drivers/vfio/vfio_main.c
@@ -414,6 +414,7 @@ vfio_allocate_device_file(struct vfio_device *device)
 		return ERR_PTR(-ENOMEM);
 
 	df->device = device;
+	spin_lock_init(&df->kvm_ref_lock);
 
 	return df;
 }
@@ -1246,6 +1247,20 @@ bool vfio_file_enforced_coherent(struct file *file)
 }
 EXPORT_SYMBOL_GPL(vfio_file_enforced_coherent);
 
+static void vfio_device_file_set_kvm(struct file *file, struct kvm *kvm)
+{
+	struct vfio_device_file *df = file->private_data;
+
+	/*
+	 * The kvm is first recorded in the vfio_device_file, and will
+	 * be propagated to vfio_device::kvm when the file is bound to
+	 * iommufd successfully in the vfio device cdev path.
+	 */
+	spin_lock(&df->kvm_ref_lock);
+	df->kvm = kvm;
+	spin_unlock(&df->kvm_ref_lock);
+}
+
 /**
  * vfio_file_set_kvm - Link a kvm with VFIO drivers
  * @file: VFIO group file or VFIO device file
@@ -1259,6 +1274,9 @@ void vfio_file_set_kvm(struct file *file, struct kvm *kvm)
 	group = vfio_group_from_file(file);
 	if (group)
 		vfio_group_set_kvm(group, kvm);
+
+	if (vfio_device_from_file(file))
+		vfio_device_file_set_kvm(file, kvm);
 }
 EXPORT_SYMBOL_GPL(vfio_file_set_kvm);
 
-- 
2.34.1